Electronic tube



1944. 'r. A. COHEN ELECTRONIC TUBE Filad Jan. 22. 1942 2 Sheets-Sheet 177moa0m 4. Col: m, vmo WM A fl'orn ey Aug. 1, 1944. 'r. A. COHENELECTRONIC TUBE Filed Jan. 22, 1942 2 Sheets-Sheet 2 VIII III

Theodore A (0/: en, mvmon, BY M X/ A ffarn e Patented Aug. 1, 1944ELECTRONIC TUBEv Theodore A. Cohen, Chicago, Ill., assignor, by mesneassignments, to Wheelco Instruments Company, Chicago, 111., acorporation of Illinois Application January 22, 1942, Serial No. 427,794

9 Claims. (Cl. 250-275) This invention relates to electronic tubes ingeneral and more particularly to such tubes wherein a high degree ofsensitivity and dependability is required.

In electronic tubes for use in electronic appa ratus requiring a highdegree of sensitivity and dependability of operation, e. g., when usedin connection with automatic burner control apparatus, vacuum tubevoltmeters, measuring apparatus, television, etc., leakage between thecontrol and controlled elements, within or without the tube enclosure,would be apt to cause the tube to function erroneously.

It is accordingly the primary object of this invention to provide anelectronic tube, and method of making the same, wherein leakage betweenthe control and controlled electrodes is minimized and such as remainsis rendered ineilective.

Other and further objects of this invention will become more apparenthereinafter as the same becomes better understood from an examination ofthe specification and claims in conjunction with the accompanyingdrawings wherein:

Fig. 1 is a vertical sectional view, partly frag mentary, and withcertain parts in elevation, showing an electronic tube embodying thisinvention;

Fig. 2 is a similar view showing a modified form of the invention; and

Fig. 3 is a horizontal sectional view taken at the line 33 of Fig. 2.

Referring to the drawings more particularly, reference character Idesignates an envelop of a vacuum tube having a stem 2 and base 3. Asupport rod 4 in the stem supports a cylindrical cathode 5 within whichis mounted a conventional cathode heater 6 (shown fragmentarily) in theusual manner.

Instead of the usual mica intersupport between the plate grid andcathode with its attendant leakage path and resultant bad effect uponthe sensitivity or dependable operation of the tube, I provide anannular mica disc I which acts as a separator between cathode 5 andplate support rod 8, said disc being fitted to said cathode and lockedtocollars I! mounted at the top of plate support rods 8. A secondannular insulating disc I is also fitted, at its inner periphery, I

to cathode and has its outer margin locked to collars (similar'to I'I)mounted at top of grid support rods II. A conventional spiral grid I2 issuitably attached to grid support rods II. A metal separator ring I5 isalso fitted around cathode 5 and contacts both mica separators I and I0whereby any leakage path which may be present between plate and gridalong said separators is contacted at an intermediate point by said ringwhich is at cathode'potential. Therefore any leakage path is split intotwo components which are respectively distributed in parallel with thegrid cathode load and the plate cathode load, such distributionresulting in counteraction between the grid-cathode leakage effectandthe plate cathode leakage effect and thereby making the plate-gridleakage resistance inefiective to cause erroneous function in the tubecircuit system.

A similar arrangement is provided at the bottom of the electrodestructures comprising an annular mica separator disc Ia fitted tocathode 5, at the lower end thereof, and attached to lock collars I'Iaat the lower end of plate support rods 8. A mica separator Illa likewiseis fitted to cathode 5, near the lower end thereof, and said separatoris attached to lock collars on the lower end of grid support rods II. Ametal separator ring I5a is fitted to the lower end of cathode 5 andacts to contact any leakage path which may be present between plate andgrid along separators Ia and Illa to bring said path to cathodepotential to render such leakage ineffective.

Metal wire elements 9 in stem 2 extend upwardly to support rods 8.

A grid lead I3 extends from one of the metallic grid supports IIdownwardly through an aperture in disc Ia to a conductor I4, throughstem 2, to a grid base lead 25, the latter leading to a grid base prong28.

Sealing cement 23 acts to seal the envelop I in base 3.

A plate base lead 24 extends from one of the plate support wires 9 toplate base prong 29.

A cathode base lead 26 extends from one of the cathode support rods 4 toan annular base shield 21 around grid prong 28 and this shield is inturn connected to a cathode prong 30. Thus any leakage path that may bepresent in the base, or below, between plate lead 24 and grid lead 25 orbetween plate prong 29 and grid prong 2B is bound to be contacted byshield 21 which is at cathode potential whereupon such leakage will berendered ineffective.

'In order to minimize the leakage in the tube which results from thedeposit of getter salts, during the manufacture of the tube, the getter22 is mounted between a mica getter flash shield I8 and the upper innerend of the envelop I with said shield between the getter and theelectrodes (including their supporting structure). The shield I8 ismounted on support studs I6 attached to and extending upwardly from disc'I and is provided with perforations I9 so that the getter function inthe process of exhausting the tube envelop of gases during manufacturewill not be confined to the upper portion of the envelop above theshield. A getter cap support rod 20, preferably centrally mounted on theshield I8 and a getter cap 2| supports the getter 22 Referring to themodification shown in Figs.

2 and 3, the intersupporting structure between plate, cathode and grid,likewiseprovides an intermediate contact to any leakage path which maybe present between plate and grid, which contact is connected to a tubeprong for contacting a portion of an external circuit for rendering suchleakage ineffective. As here shown, reference character 3| designates acylindrical cathode having a conventional heater 32 (shownfragmentarily). A conventional spiral grid 33 surrounds said cathode andis supported by rods 34. A 'cylindricalplate 35, supported byrods 36,surrounds saidgrid. Three concentric circular spaced mica separator discportions 3'lq, 31b and Nears connected together in the same plane andform an upper supporting disc 31 for the electrodes. Disc 31 is attachedto cathode 3| and the upper ends of grid support rods 34 and platesupport rods 36, disc portion 31a being attached to said rods 36, discportion 311) being attached to said rods 34 and disc portion 310 fittingaround cathode 3|. Disc portions 31a and 310 are connected to inner discportion 31b by metal concentric shield rings 40 and 39, respectively.These metal shield rings are connected together by suitable conductors42 which lead to a shield ring conductor 43 which may pass throughthe'stem to a suitable'prong for contacting an external circuit atadesired potential relative to the cathode or to the cathode, as before,for rendering the leakage in the tube between plate and gridinefiective; Conductor 43 and prong therefor may be connected to. eitherthe cathode or a predetermined potential in the circuit in-which thetube may be used. Such predetermined potential may be a neutral point insaid circuit or a neutralizing potential for overcoming the leakageeffect of the aforesaid leakage path efiect upon said circuit.

The bottom supporting structure comprising a lower supporting disc 38and concentric metal shield rings 39a and 40a is exactly similar to thatdescribed above except that it is attached to the bottom of cathode 3|and rods 34 and 36 instead of to the top thereof as in the case of theupper supporting structure. These shield rings 39a and Mia also lead tothe common shield ring conductor 43.

'In this modification the same getter shield and support andthe samebase lead and prong shield, which for brevity are not duplicated in thisillustration, are also preferably used. 7

The advantages and operation of. the aforedescribed tubeswill beapparent without further description and I am aware that many changesmay be made without departingfro'm the principles of this invention andI therefore do not wish to be limited to" the details' shown ordescribed. 1

' Iclaim:

' 1. An electronic tube comprising a controlled and a control electrode;intersupportingstructure for said electrodes provided with rneans,therbetween, for contacting any leakage path and connectingthe same to apredetermined potential, an envelop enclosing said'electrodes' andstructure and a getter shield 'separatinga portion of the interior ofsaid envelop from said structure, with the gettensupported in saidseparated portion for minimizing the leakage path which may result fromthe deposit of getter salts on said structure.

2. An electronic tube comprising a controlled and a control electrode,intersupporting structure for said electrodes, an envelop enclosing saidelectrodes and structure and a uniformly perforated getter shieldseparating a portion of the interior of said envelop from saidstructure, and a getter supported in said separated portion forminimizing the leakage path which may result from the deposit of gettersalts on said structrue.

3. An'electronic tube comprising a pair of concentrically mountedelectrodes, concentric dielectric discs attached to the respectiveelectrodes, a concentric metallic ring separating said discs andcontacting the cathode for rendering any leakage between the electrodesineffective.

4. An electronic tube comprising a pair of concentrically mountedelectrodes, a centrally mounted cathode, concentrically mounteddielectric discs, one attached to each of said first electrodes andfitted around said cathode and a concentric metallic ring separatingsaid discs and also fitted around said cathode for contacting anyleakage path between said electrodes and connecting the same to saidcathode for rendering such leakage inefiective.

5. An electronic tube comprising a pair of concentrically mountedelectrodes, a centrally mounted cathode, concentrically mounteddielectric discs, one attached to each of said first electrodes and aconcentric metallic ring separating said discs and connected to saidcathode for contacting any leakage path between said electrodes andconnecting the same to said cathode for rendering such leakageineffective.

6. An electronic tube comprising a pair of concentrically mountedelectrodes, a centrally mounted cathode, concentric dielectric discsattached to the first electrodes and an intersupporting annular metallicmember separating said discs and connected to said cathode forcontacting any leakage path between said electrodes and connecting thesame to said cathode for rendering such leakage inefiective.

7. An electronic tube comprising a cathode, concentrically mountedelectrodes, concentric dielectric discs attached to the respectiveelectrodes-a concentric metallic ring separating said discs, said ringconnected to said cathode for contacting any leakage path between saidelectrodes and connecting the same to said cathode for rendering suchleakage ineffective.

8. An electronic tube comprising a cathode, a controlled electrode, acontrol electrode,-and intersupporting structure for said electrodesprovided with a metallic ring separating such structure and fittedaround said cathode for contacting any leakage path in said structurewhich may be present between said electrodes and for connecting the pathto said cathode, for rendering such leakage ineffective.

9. An electronic tube comprising a plate, grid and cathode andintersupporting-structure therefor provided with a concentric metallicring separating said structure between the plate and grid for contactingany leakage paththere-between and fitted around said cathode forconnecting such-path thereto. u

e I THEODORE A. COHEN;-

